Internal antistatic agent for super polyamides and polyamide compositions having improved antistatic property

ABSTRACT

AN INTERNAL ANTISTATIC AGENT FOR SYNTHETIC POLYAMIDE USE WHICH COMPRISES A COMPOUND WHICH IS AN ADDITION PRODUCT OF AN ALKYLENE OXIDE AND A CARBONAMIDE GROUP-CONTAINING COMPOUND CONTAINING A STRUCTURAL UNIT OF THE FORMULA   -CO-N(-(A,B)N-H)-   WHEREIN A STANDS FOR ETHYLENEOXIDE B STANDS FOR PROPYLENEOXIDE, $A,B$N STANDS FOR A HOMOPOLYMER OF ETHYLENEOXIDE OR PROPYLENEOXIDE OR A BLOCK OR RANDOM COPOLYMER OF ETHYLENEOXIDE AND PROPYLENEOXIDE AND N IS AN INTEGER FROM 10 TO 1000.

ABSTRACT OF THE DISCLOSURE An internal antistatic agent for synthetic polyamide use which comprises a compound which is an addition product of an alkylene oxide and a carbonamide group-containing compound containng a structural unit of the formula wherein A stands for ethyleneoxide B stands for propyleneoxide, {-A,B stands for a homopolymer of ethyleneoxide or propyleneoxide or a block or random copolymer of ethyleneoxide and propyleneoxide and n is an integer from to 1000.

This invention relates to a new internal antistatic agent for synthetic polyamide use and also to the synthetic polyamide composition containing said antistatic agent.

In general, the synthetic fibers possess such characteristics as durability, tenacity and chemical inertness but, on the other hand, their insulation resistance being high, they have a tendency to become charged with static electricity. Hence, this becomes a serious matter during the production of textile materials or in wearing clothes made of such statically charged material.

As a method of preventing this electrification of the synthetic fibers, heretofore, it has been the general practice, for example, to effect the adhesion to the surface of the synthetic fibers of a surfactant which has an antistatic property, but the effect of most of these antistatic agents are only temporary and are lacking in durability. Further a fabric which has been coated with an antistatic agent, which has been imparted durability by being insolubilized or fixed on the surface of the textile, generally has an unsatisfactory hand and hence becomes a fabric lacking in appeal. Accordingly, the idea that it might be possible to solve this problem by using the antistatic agent incorporated in the synthetic fiber is one which is readily conceivable by all. However, an antistatic agent which gives excellent antistatic property without any adverse effects on the spinnability and quality of the fiber upon being actually incorporated is not readily obtainable. There are one or two patent literatures which disclose antistatic agents directed to such a purpose, but there does not seem to be any which have actually been put to practice.

For example, a method, as disclosed in British Patent No. 963,320 and US. Pat. 3,329,557 is known wherein a compound which has been obtained by effecting the bond of one end of polyethylene oxide with a hydrophobic group by means of an ether bond is mixed with a super polyamide and this mixture is to be spun. But the spinning of this mixture is quite difficult and does not give sufficiently uniform yarn, because of such drawbacks as that phase separation of this mixture occurs during Spinning,

United States Patent Oflice 3,557,060 Patented Jan. 19, 1971 or that the chips of the mixture are not satisfactorily caught into screw of the extruder.

Also known is a method of mixing the super polyamides with a phosphorus amide or salts of metals other than alkali (e.g. Ca and Mg) with other nitrogen-containing compounds, but in this case the discoloration is frequently excessive and hence there is the drawback that the fibers obtained cannot be used for clothing purpose wherein white materials are required.

We found that when a specific addition product, which comprises a specific compound having a carbonamide bond and an alkylene oxide, were incorporated in a super polyamide, the hereinbefore described troubles did not appear in the manufacture and processing of shaped articles of super polyamides and furthermore that an excellent antistatic effect was imparted to the polyamides without imparing the quality of the shaped articles.

According to this invention, an internal antistatic agent for super polyamide use is provided which comprises a compound which is an addition product of an alkylene oxide of 2 to 3 carbon atoms and a carbonamide groupcontaining compound selected from the group consisting of lactams whose ring are formed by 3-12 carbon atoms, oligomers up to hexamers of said lactams, low molecular weight polycondensation products up to hexamers of waminocarboxylic acids of 3-12 carbon atoms, low molecular weight polycondensation products of a molecular weight less than 3000, and up to hexamers of dicarboxylic acids and diamines, said addition product containing a structural unit of the formula I O=(|J N/A, B\ H wherein A stands for ethyleneoxide, B stands for propyleneoxide, fABi stands for a homopolymer of ethyleneoxide or propyleneoxide or a block or random copolymer of ethyleneoxide and propyleneoxide, and n is an integer from 10 to 1000.

Further, the invention provides polyamide compositions whose antistatic property has been improved as a result of having been incorporated with 0.1 to 10 parts by weight of the aforesaid antistatic agent per parts by weight of said super polyamide.

As the carbonamide group-containing compound to be used in the invention, included are lactams whose ring are formed by 312 carbon atoms, oligomers up to hexamers of said lactams, low molecular weight polycondensation products up to hexamers of w-aminocarboxylic acids of 312 carbon atoms or low molecular weight polycondensation products of a molecular weight less than 3000 and up to hexamers of dicarboxylic acids and diamines, or the mixture of these. As the foregoing lactams, useable are the lactams of the formula wherein R is hydrogen or alkyl radical and n is a number from 1 to 10, particularly preferred being e-caprolactam, capryllactam and laurolactam. Of the foregoing lactams, the oligomers of the polymerizable lactams, i.e. the oligomers of lactams whose degree of polymerization is from 2 to 6 can also be used in the invention. These oligomers may either be those of cyclic or chain configuration. Those having a degree of polymerization from 24 are particularly to be preferred in the invention. The oligomers of e-caprolactam or the mixtures thereof are especially desirable from the standpoint of the utilization of by-products, since they are available as by-products in the process of producing 6 nylon.

As the low molecular weight polycondensation products of dicarboxylic acids and diamines, those of the fol lowing structural formula are used:

wherein R" and R' are each a hydrocarbon residue of 2-25 carbon atoms or an alkylene group having a cyclic or hetero atom, and m is a number from 1 to 6. Suitable diamines are exemplified by such as hexamethylenediamine and m-xylylenediamine, while examples of suitable dicarboxylic acids include such as adipic, sebacic, dodecandioic and isophthalic acids.

As in the case with the oligomers of lactams, the low molecular weight polycondensation products of the waminocarboxylic acids such, for example, as w-aminoundecanoic acid, w-aminoheptanoic acid and w-aminocaproic acids can also be used.

The alkylene oxides include such, for example, as ethylene oxide, propylene oxide, and the mixture of ethylene oxide and propylene oxide.

As a method of adding the alkylene oxide to the aforesaid carbonamide group-containing compound, any method may be used. For instance, the alkylene oxide is addition-polymerized to the carbonamide group-containing compound in customary manner in the presence of an acid or alkali catalyst at, say, a temperature of 140 C. and a pressure of 3 atmospheres. The foregoing methods do not limit this invention, however. Again, the alkylene oxide can be added in the singular, random or block form.

The number of moles of the alkylene oxide added may be chosen optionally in accordance with the objective desired but generally a better antistatic property is demonstrated in the case of the higher moles of addition products. Hence, while there will be differences depending upon the class of the alkylene oxide, generally speaking, the use of to 1000 mole equivalents, and especially suitably 20 to 500 mol equivalents, of the alkylene oxide, based on the carbonamide group of the aforesaid carbonamide group-containing compound is to be preferred.

The invention antistatic agent thus obtained has in its molecules at least one structural unit of the formula Ozi i T wherein the groups A, B in the oxyalkylene block may be the same or different throughout the whole block. For example, the oxyalkylene block may be constituted of either polyoxyethylene, an oxyethylene/oxypropylene random copolymer, or a polyoxyethylene/polyoxypropylene block copolymer.

The invention antistatic agent is incorporated in the synthetic linear super polyamide in an amount of 0.1 to 10% by Weight, and preferably 0.5 to 5% by weight, based on the polyamide.

As the synthetic linear super polyamides to which the invention antistatic agent is applicable, included are the usual super polyamides such as 6 nylon (poly-w-caprolactam), 66 nylon (polyhexamethylene adipamide), 7 nylon (poly-w-aminoheptanoic acid), 8 nylon (polycapryllactam), 9 nylon (poly-w-aminononanoic acid) 6, 1O nylon (polyhexamethylene sebacamide), 11 nylon (poly-waminoundeeanoic acid) and 12 nylon (polylaurolactam); polyamides having an aromatic ring such as polyamide obtained from p-xylylenediamine and dodecandioic acid; and other polyamides having in their main chain an ether bond, or an alicyclic or heterocyclic ring.

According to the invention, the aforesaid antistatic agent must be mixed homogeneously in these super polyamides. Thus, in this invention the antistatic agent is mixed in the polyamides before the latter are molded. For example, the super polyamide chips and the antistatic agent are first blended in an extruder, then the antistatic agent is dispersed uniformly by melting the mixture, and thereafter the mixture is extruded and made into filaments. Also useable is the master batch technique which is carried out in the following manner. A master chip is prepared which contains the antistatic agent in a high concentration."Next, this is mixed with polyamide chips to which the antistatic agent has not been added to accomplish the dilution of the mixture to the desired concentration thereby obtaining a mixture and hence products in which the antistatic agent is well dispersed. Alternatively, the polyamide chips can be treated with the antistatic agent dissolved in a solvent to effect the uniform blending of the antistatic agent with the polyamide chips, followed by removal of the solvent and spinning of the chips in customary manner. Again, the antistatic agent can be added to the monomer during the polymerization reaction, if necessary. Further, in the case of this method in which the antistatic agent is added during the polymerization reaction, a more uniform dispersion can be obtained than in the case where the antistatic agent is mixed with the chips. Moreover, it can be said to be more economical since an extra step is eliminated.

The polyamide compositions containing the invention antistatic agent can be readily formed into fiber, film, sheet, rod tube, casting and other articles by means which are generally known. An especially satisfactory antistatic effect can be manifested when the invention polyamide composition is formed into fibers.

As a result of the incorporation of the invention antistatic agent in the polyamide, a marked decline in the insulation resistance of the shaped article takes place, and not only can a pronounced electrification be avoided semipermanently but also the extent to which the electrification phenomenon is affected by the humidity surrounding the shaped article is reduced. Hence, in the case of the so obtained filaments or staples, the troubles during their processing which are ascribable to static electricity can be eliminated. Moreover, the disagreeable phenomena such as attraction of dust and sparking which occur during wearing of clothes made from textile materials obtained by weaving these fibers can be prevented.

This antistatic effect does not decline with the passage of time, and furthermore this effect can not only withstand laundering but also its decline under harsh dry cleaning conditions is also small.

In addition, the invention antistatic agent possesses an excellent thermal stability. It withstands the elevated temperatures which are encountered during the manufacturing and processing steps of the polyamide shaped articles, and even when mixed with the polyamide it does not have an especially adverse effect on such textile product production steps of spinning of the filaments, drawing, spinning of staples, weaving and knitting, there being noted no substantial change in the physical properties and coloration of the products.

The invention antistatic agent can be used in conjunction with antioxidant, delustrants, pigments and similar substances without its antistatic property being substantially affected.

The fact that the invention antistatic agent comprising an addition product of a carbonamide group-containing low molecular weight compound and an alkylene oxide does not adversely affect the manufacturing operations of shaped articles even when incorporated in the poly amide, as hereinabove described, and furthermore imparts a durable antistatic property to the polyamide while substantially maintaining its excellent physical properties is truly surprising. For example, when a polyalkylene oxide is merely mixed and spun with a polyamide, the phase separation of the two components take place to greatly reduce the spinnability and, in addition, the antistatic property of the resulting fiber is as yet unsatisfactory. On the other hand, when the polyalkylene oxide is used in the form of an addition product of the aforesaid carbonamide group-containing low molecular weight compound, all of the above-described drawbacks are solved and, in addition, an excellent antistatic property is developed. This is conceivably the result of the afiinity between the polyamide and the carbonamide group-containing low molecular weight compound portion of the invention antistatic agent.

The following examples are given for further illustration of the invention. Unless otherwise specified, the parts and percentages in the following examples are on a weight basis.

EXAMPLE 1 Ethylene oxide in the amounts of respectively 660, 1320 and 2640 parts were addition polymizered to 113 parts of e-caprolactam in customary manner at a reaction temperature of ISO-180 C., a reaction pressure of 4-5 kilograms per square centimeter and a reaction time of 4 hours. Ten parts each of three classes of antistatic agents (molecular weights 773, 1433 and 2753) were mixed respectively with 100 parts of polycaprolactam chips (inherent viscosity 2.45) to prepare by the master batch method chips containing the antistatic agents in high concentration. This was followed by mixing the so obtained chi s uniformly with unmodified chips not containing the antistatic agent such that the concentration of the antistatic agent would become 2%, using a blender, following which the mixtures were melt-spun in customary manner using a melt-spinning machine. The freshly drawn filaments were drawn about 4 and multifilaments (30 total denier, filaments) were prepared, from which were then knit tricots A, B and C.

Further, tricot D was made in like manner from unmodified chips to which the antistatic agent had not been added. The so obtained four classes of test specimens A, B, C and D were subjected to four cycles of harsh laundering followed by ironing at the usual temperature after each cycle. The results of the antistatic performance, as evaluated by the frictional electrification voltage, of tricots A, B, C and D after the four cycles of washing and pressing as well as their voltage measurements before laundering are shown in Table I.

The measurements were made at a temperature of 20 C. and a relative humidity of 55%, the several specimens being measured 48 hours after they were adjusted to the same temperature and humidity. A rotary static tester (a product of Koa Shokai, Ltd., Japan) was used and the voltage of frictional charge was measured in customay manner by mounting the tricot specimen to the rotating drum and causing it to rub at a speed of 452 meters per minute with a polyethylene terephthalate film suspended with a 20-gram load, and measuring the electric charge generated.

As can be seen from these results, the tricot A, B and C in which had been incorporated the invention antistatic agent were observed to maintain their antistatic property fully even after their laundering. Further, it was noted that in the case of tricot A whose amount added of ethylene oxide was less the antistatic effect was slightly inferior than that of tricots B and C where the amount added of the ethylene oxide was greater.

EXAMPLE 2 A 1:5 (weight ratio) mixture of propylene oxide and ethylene oxide was added randomly to e-caprolactam in customary manner (reaction temperature 100-130 C., reaction pressure 2-3 kilogram per quare centimeter, reaction time 10 hours) and two classes of soft, light yellow compounds of molecular weights about 3000 and 6000 were prepared.

2.5 parts of each of the so prepared antistatic agents were added respectively to 100 parts of polyhexarnethylene adipate (inherent viscosity 2.56) and after blending the mixtures uniformly, they were pelletized using a screw extruder. Filaments A and B (100 total denier, 24 filaments) were made in customary manner by spinning these pellets and thereafter drawing the freshly spun filaments 4X.

In like manner, an unmodified control specimen not containing the antistatic agent was made.

These three classes of filaments were then submitted to a warping test at a warping speed of 200 meters per minute using a small-size warper and the voltage of the electric charge generated by the filaments travelling between the reeds was measured at a height of 10 cm. with a current collecting type electric potential measuring apparatus (a product of Kasuga Denki Co., Ltd., Japan), with the results shown in Table II.

TABLE II Voltage of electric Molecular charge weight of the genera(ted antistatic agent S p ecimen About 3,000. About 6,000.

EXAMPLE 3 To the residue remaining after recovering the lactam from the extraction water of the 6 nylon pellet production step was added water in a tenfold amount. This was then heated, filtered while still hot and thereafter the filtrate was cooled. To the precipitate then obtained was again added water, which was heated and cooled to obtain a precipitate. To parts of the purified product of an oligomer (degree of polymerization 2-3) of caprolactam was addition polymerized ethylene oxide in the amounts of respectively 1000 and 1500 parts in customery manner (in the presence of an alkali catalyst, at a reaction temperature of l30-l50 C., a reaction pressure of 3-4 kilograms per square centimeter and a reaction time of 7 hours) thereby obtaining two class of light yellow, solid reaction products.

Next, as in Example 2, 2.5 parts of the foregoing antistatic agent were added to 100 parts of polycaprolactam chips, blended uniformly and pelletized, after which the pellets were spun into filaments and drawn. The so obtained filaments were then cut and staples A and B were prepared.

Both had a denier number of 3 and a cut length of 51 mm. Unmodified control staple C not containing the antistatic agent was prepared in like manner. Next, carpets A, B and C were made in customary manner via the processes of dyeing, spinning, and weaving. The so obtained carpet specimens A, B and C were then washed with a commercial non-ionic detergent followed 'by washing with water and drying. They were then adjusted as to their humidity and measured for their insulation resistance. The results obtained are shown in Table III.

TABLE Ill Amount added Insulation of ethylene Oxide 8 EXAMPLE 1/350 moles of acetic acid and 2% of the ethylene oxide added e-caprolactam obtained in Example 1 were Specimen tiz of added to 15% Water-containing lactam, and the polym- 5X10) 1 000 5 erization reaction was carried out in a polymerization g: ":1: 4x10 500 kettle for 16 hours at 260 C. The resulting chips are spun Carpet 0 Above 10 0 and drawn 4x in customary manner to obtain a drawn multifilament (30 total denier, 10 filaments).

It Was noted the antlstatlc Property of carpets A This multifilament is knit into a tubular knit fabric, and B wassuperior to that of carpet C. The temperature 10 which is Washed four times in a 0.2% detergent liquid and and humldlty at Whlch the measurement was made was thereafter measured for its antistatic performance. The 19 C. and 60% RH, and the measurement was made results obtained are shown inTab1ev using a Super Megohm-meter Model SM-5 (a product TABLE v of Toa Dempa Kogyo Co., Ltd., Japan).

Further, there was noted no substantial difference be- Amount Voltage r added of electric tween carpets A, B and C as far as their processes of ethyiene charge (VJ oxide aft manufacture were concerned. Specimen (part) was;

EX P 4 gugularinig P1131101]; 1 660 110-130 20 'r b i k tr b c 2 640 60-80 For facilitating the addition of the alkylene oxide, 9 g g gg gi D i 0 2,00% 000 parts of ethylene oxide were added to a mixture of 80 parts of the oligonier of Example 3 and 20 parts of 6- EXAMPLE 6 caprolactam followed by the addition of 100 parts of propylene oxide, thereby obtaining a light yellow, soft A11 yl OXlde added p f l deflvatlve reaction product (molecular weight 2422). lecular weight 8943) was made by addition polymerizing Next, 0.5 and 3 parts of the so obtained antistatic 9 garts lm/510 OXlde to $1 p g d d p g f g agent were added respectively to 100 parts of polycapro- In p e 1 C mpQun was a e to an mixe lactam having an inherent viscosity of 2.45, following With p y' p l? (Inherent VISCOSIIY which these were uniformly mixed with a blender. The so in a p p ion Of 3%, and th mixture Was then meltobtained mixtures were then pelletized using an extruder, p n- Th r y p n filaments W wn t0 and thereafter the resulting pellets were melt-spun in yield filament A. customary manner. In like manner, polyethylene glycol of an average mo- This was followed by drawing the freshly spun filalecular We1ght100f0 $18 adieil1 to pgly-e-caprolactam chips ments at a draw ratio of 4 to obtain a multifilament in a ro ortion o 3 0 an t erea for s um and drawn as yarn (75 total denier, 36 filaments), after which plain hereir ibe f ore described to obtain filament B. weave taifetas A and B were woven in customary man- On the other hand, 16.7% by weight of an adipic acid ner. In like manner, taffeta C was woven prepared from salt of diamine containing polyethylene oxide of an averan unmodified polymer not containing the antistatic agent. age molecular weight of 1000 was mixed with e-capro- Next, the specimens of the fabrics to be tested were lactam and the polymerization reaction was carried out washed for one hour under boiling conditions in a 0.5% while mixing the mixture uniformly at 280 C. The resultaqueous solution of sodium salt of higher unsaturated ing polymer was melt-spun at 260 C. in customary manalcohol sulfate followed by water-washing and drying. ner and filament C was obtained.

One side of the so obtained tafietas A, B and C were The properties of each of the foregoing filaments were rubbed under given conditions with gauze and then compared. The results obtained are shown in Table VI, brought into proximity of fresh tobacco ash and the debelow.

TABLE VI Yarn properties Young's modulus 'Iliennal Aiitistatic [)UCIHICII pinna l l y g. T0515 an 6 proper y s s b'l't (/d) t e t 2 Filament A... No particular problem 40 200 Filament B Occurence of filament breaks due 39 55 900 to phase separation. Filament C Spinning under ordinary condi- 3 9 10 150 tions difficult due to fusion.

1 Rate of tenacity maintenance at 130 C. (percent)]. 2 Voltage of frictional charge after washing). 3 Further marked drop upon heat treatment.

gree of attraction was compared. The results obtained are shown in Table IV.

TABLE IV Amount added of antistatic agent Specimen Degree of attraction of tobacco ash (part) Taffeta A Attraction phenomenon is noted at a 0. 5

height of 4 cm., but the ash falls away upon flicking the specimen lightly. Talleta B Attraction phenomenon is hardly noted 3 even at a height of 1 cm. 'lalieta C Pronounced attraction takes place at a 0 height of 8 em. The ash does not fall away easily even when Nicki-d lightly.

EXAMPLE 7 1) One percent by weight of metallic potassium was added at about C. to distilled n-pyri'olidone in a stream of dried N After the polymerization reaction was carried out for 12 hours, the polymeric mass was comminuted (polymer A).

(2) w-Aminoundecanoic acid was polymerized for hours in a stream of N and, after cooling in the N stream, the polymer was taken out (polymer B).

(3) A 6,6 salt was prepared in customary manner from hexamethylene diamine and adipic acid, following which this salt was heated for 1.5-2 hours at 215 C. in a polymerization tube. After cooling to room temperature, purging with N was repeated several times and thereafter the salt was heated at 270 C. An hour later, further heating for one hour was carried out at a reduced pres.- sure of 0.2-1.5 mm. Hg. After cooling, a white opaque polymer was separated (polymer C).

To each of the so polymerized polymers A, B and C was added water in a tenfold amount followed by heating and hot filtration, and thereafter cooling of the filtrates. To the obtained precipitates water was again added, followed by heating, cooling and obtaining of precipitates. To 100 parts of the so obtained purified products of the several oligomers (degree of polymerization 2-3) were addition polymerized in customary manner respectively 1000 parts of ethylene oxide under the conditions such as given in Example 3, thereby obtaining three classes of solid reaction products. As in Example 2, 2.5 parts of each of these reaction products were added to 100 parts of poly-e-caprolactam chips (inherent viscosity 2.56), after which the mixtures were pelletized. These pellets were spun in customary manner and the freshly spun filaments were drawn about 2.5x thereby obtaining multifilaments (30 total denier, 10 filaments). After knitting these multifilaments into tubular knit fabrics, the resulting fabrics were washed four times in a 0.2% detergent solution. When the washed fabrics were tested for their antistatic performance, the results shown in Table VII were obtained.

TABLE VII Voltage of electric charge (v.) Specimen: oligomer derivative of polymer- A 150 B 180 C 160 We claim: v

1. A fiber forming synthetic linear saturated aliphatic polycarbonamide composition having an improved antistatic property, said composition consisting essentially of 0.1 to 10 percent by weight, based on said polycarbonamide, a homogeneously distributed compound which is an addition product of an alkylene oxide of 2 to 3 carbon atoms and a carbonamide group-containing compound selected from the group consisting of lactams whose ring is 3-12 carbon atoms, oligomers up to hexamers of said lactams, low molecular weight polycondensation products up to hexamers of w-aminocarboxylic acids of 3-12 carbon atoms, said addition product containing a structural unit of the formula wherein X stands for ethyleneoxide, Y stands for propyleneoxide, (X, Y). stands for a homopolymer of ethyleneoxide or propyleneoxide or a block or random copolymer of ethylene oxide and propyleneoxide and n is an integer from 10 to 1000.

2. A composition according to claim 1 wherein said synthetic polyamide is selected from the group consisting of polycaprolactam and polyhexamethylene adipamide.

3. A fiber of the composition of claim 1.

References Cited UNITED STATES PATENTS 2,835,653 5/1958 Haas et al 26078 2,998,295 8/ 1961 Goldann 26078 3,038,885 6/1962 Best 26078 HAROLD D. ANDERSON, Primary Examiner US. Cl. X.R. 

